Prognostic roles of KL‐6 in disease severity and lung injury in COVID‐19 patients: A longitudinal retrospective analysis

To investigate the dynamic changes of Krebs von den Lungen‐6 (KL‐6) among patients with coronavirus disease 2019 (COVID‐19) and the role of KL‐6 as a noninvasive biomarker for predicting long‐term lung injury, the clinical information and laboratory tests of 166 COVID‐19 patients were collected, and a correlation analysis between KL‐6 and other parameters was conducted. There were 17 (10.2%, 17/166) severe/critical and 149 (89.8%, 149/166) mild COVID‐19 patients in our cohort. Serum KL‐6 was significantly higher in severe/critical COVID‐19 patients than in mild patients (median 898.0 vs. 451.2 U/ml, p 100 days postonset) was well correlated to those concentrations within 10 days postonset (Pearson r = .867, p